S. Intarasiri

Effects of low-fluence swift iodine ion bombardment on the crystallization of ion-beam-synthesized silicon carbide

Ion beam synthesis using high-fluence carbon ion implantation in silicon in combination with subsequent or in situ thermal annealing has been shown to be able to form nanocrystalline cubic SiC (3C-SiC) layers in silicon. In this study, a silicon carbide layer was synthesized by 40-keV C12+ implantation of a p-type (100) Si wafer at a fluence of 6.5×1017 ions∕cm2 at an elevated temperature. The existence of the implanted carbon in Si substrate was investigated by time-of-flight energy elastic recoil detection analysis. The SiC layer was subsequently irradiated by 10–30 MeV I127 ions to a very low fluence of 1012 ions∕cm2 at temperatures from 80 to 800 °C to study the effect on the crystallization of the SiC layer. Infrared spectroscopy and Raman scattering measurement were used to monitor the formation of SiC and detailed information about the SiC film properties was obtained by analyzing the peak shape of the Si-C stretching mode absorption. The change in crystallinity of the synthesized layer was probed ...

Ion Beam Synthesis of Silicon Carbide

Formation and crystallization of a thin near-surface layer of silicon carbide on a silicon substrate, created by ion-beam synthesis (IBS), are discussed. 80 and 40 keV carbon ions were implanted into a (1 0 0) high-purity p-type silicon substrate at room temperature and 400 oC, respectively, using doses in excess of 1017 ions/cm2. Elastic recoil detection analysis (ERDA) technique, developed for routine atomic depth profiling at the Angstrom laboratory, Uppsala University, Sweden, was used to investigate the depth distributions of implanted-ions. Infrared transmittance measurement was used as an indication of SiC in the implanted Si substrate. For the samples implanted at high temperature, the results show the existence of a peak at 797 cm-1, indicating the presence of β-SiC, already directly formed during the implantation without postimplantation annealing. While for the samples implanted at room temperature, starting with the band of amorphous Si-C network, the crystalline SiC appears at the annealing temperature as low as 900 oC. In both cases, during further annealing in vacuum, the peak grows in height and narrows in width (according to the measured FWHM) with increasing annealing temperature, indicating a further growth of the SiC layer. However, for thermal annealing at 1000 oC in a vacuum furnace the SiC crystallization was not completed and crystal imperfection where still present. Complementary to IR, Raman scattering measurements were performed. Although no direct evidence of SiC vibrations were observed, the appearance and disappearance of both Si-Si and C-C related bands points out to the formation of silicon and carbon clusters in the implanted layer.

Ion implantation modification of special steels in Thailand

Abstract Various ion implantation methods, including using focused high-density and scanning beams, mixing B-ions to implanted N-ion layers and assisting normal N-ion implantation with both preparative and closing implantations, have been recently developed for modification of special steels in the ion beam center at Chiang Mai University in Thailand. Tool, machinery and structural steel samples in a hardened or unhardened state have been ion-beam-treated. Experimental evidence shows increases in microhardness and improvements in wear resistance for the implanted steels and some particularly impressive modifications. Comparisons are made for ion implantation effects on the tribological property modification of the hardened and unhardened steels between wear conditions of hard ball with heavy load and soft ball with light load. The results indicate that scanning high-density beam N-ion implantation has a potential in strengthening hardened steels, but with a dependence on the Cr as well as C contents, and additional B-ion implantation and multiple N- and B-ion implantation can also effectively strengthen the hardened steels.

Study of Thermal Property of Glass-Ceramics Produced from Soda Lime Glass Waste by Single-Step Sintering Process

Soda lime glass (SLG) is one type of glass mainly used in beverage and food packaging industries. SLG has high potential as starting materials for glass-ceramics (GC) production as SLG consists of large proportion of silicate and has considerably low of melting temperature. In addition, large consumption of beverages and foods, SLG makes up a large bulk of the waste. Producing glass-ceramics (GC) from SLG is thus interesting. Processing of SLG to GC is strongly dependent on their thermal property. Before processing, thermal profile of SLG was analyzed by differential scanning calorimetry; crystallization temperature at 711 °C was identified at the heating rate of 5 °C/min. It was also possible to extract information about crystallization kinetic by applying the Kissinger and the Ozawa relations. It was found that crystallization activation energies were 365.06 and 381.60 kJ/mol, respectively. For the GC processing, SLG powder was mixed with precursors to the ratio of 60SLG-35SiO2-2TiO2-2ZnO-1CuO before sintering with single step method at 711, 800, 850, 900, 950, 1,000 °C. An analysis by XRD has shown that there were two phases; beta-quartz and beta-cristobalite, in the sintered samples. Different sintering temperatures have yielded different proportion of alpha-to beta-phases. SEM/EDX has also revealed uneven distribution of different oxides in the produced glass-ceramics.

Development, Manufacturing and Characterization of a New Composite Prepared from Cyperus corymbosus Rotth and Poly(Vinyl Chloride)

This research was focused on the study of the synthesis process, and the physical and mechanical properties, of the composite material prepared from Poly(vinyl chloride) (PVC) and natural fiber extracted from reed, scientific namely Cyperus corymbosus Rotth, leading to the development of a new type of low cost material for the furniture function. Reed is chosen to be a source of natural fiber due to its ease of finding and ease of growth along water reservoir which can provide a cheap material for composite production. In the study, the samples were divided into four groups based on the addition of reed powder loading, ranged from a weight ratio of 0%, 20, 40 to 50%, respectively. The composite materials were pre-mixed, using white oil as coupling agent, by the single screw extruder, and the wood plastic was produced by compression molding method. The flat plate panels were tested by several standard techniques, including impact testing, bending testing and tensile testing. Morphology of the fracture surfaces and the dispersion of filler particles were observed by using scanning electron microscopy (SEM). The testing measurement revealed the decreasing of impact strength, tensile strength and flexural strength in all WPCs in comparison with pure PVC. This negative effect may be ascribed to the poor compatibility between the fibers and polymer matrix.

Fire Retardation Mechanism of PVC Composite Filled with White Rice Husk Ash for Ceiling Board Applications

The rising concern towards environmental issue underscores the “greenproducts” based on natural resources for a wide range of applications. Theseefforts include white rice husk ash (WRHA) considering as an alternative rawmaterial for lignocellulosic filler in green composite. We present the propertiesevaluation of composite WRHA dispersing into polyvinyl-chloride (PVC) with di-isononyl-phthalate(DINP) as compatibilizing agent by compression molding method. The XRD analysisshows typical main peak of silica crystalline, the strengthening materials asreinforcement within the composite structure. The SEM demonstrated that WRHAfillers were well embedded in PVC matrix and better adhesion occurred between themand the matrix. Thus, the adhesion between the reinforcing fiber and the matrixplays an important role in the mechanical properties of the materials. The positiveachievement for fire resistance and its mechanism were specially discussed forceiling board in/outdoor environment applications.